Ultra short wave system



Jan. 10, 1939. R. M. MORRIS ET AL 2,143,658

ULTRA SHORT WAVE SYSTEM Filed Sept. 50, 1936 2 Sheet-Sheet 1 INVENTORR.M. MORRIS AND ATTORNEY Jan. W, 1939. I R. M. MORRIS ET AL 2,143,658

ULTRA SHORT WAVE SYSTEM Filed Sept. 50, 1936 I 2 Sheets-Sheet 2[IIIITHII IIHUTUTI INVENTOR R. M. MORRIS AND C. P. SWEENY BY I ATTORNEYPatented Jan. 10, 1939 UNITED STATES PATENT OFFIC ULTRA SHORT WAVESYSTEM Application September 30, 1936, Serial No. 103,289

6 Claims.

The present invention relates to ultra short wave communication systems,and has for its primary object to provide a highly portable constructionwhich can be carried in the hand and is fairly rugged, for transmittingand/or receiving short waves of the order of one meter or less.

A further object is to provide such an improved construction which canserve in the laboratory or in the field as a source of test signals forvarious types of high frequency measurements.

A feature of the present invention lies in the excellent mechanicalandelectrical design of the structure.

In the accompanying description of the drawmgs:

Fig. 1 illustrates an exploded view of the mechanical construction ofapplicants arrangement, except for the omission of the front panel;

Fig. 2 illustrates a plan view of the lower portion of Fig. 1 with thetop removed;

Fig. 3 illustrates a cross-sectional view of Fig. 2 along the line 33;and

Fig. 4 shows the equivalent electrical circuit of applicantsarrangement, together with the essential external circuit elementsnecessary to form a complete system.

Since the same elements throughout the figures are represented by thesame reference characters, a better understanding of the invention willbe had by first referring to Fig. 4 which shows the equivalent circuitarrangement. In this figure the antenna, used either for transmitting orreceiving purposes, comprises a dipole having two arms I and 2, eachelectrically equivalent to a quarter wavelength and connected in seriesthrough a variable condenser 3 to one terminal of a parallel tunedcircuit comprising a variable condenser 4 and an inductance 5. Coupledto inductance 5 and connected in the anode circuit of electron dischargedevice oscillator I is an inductance 6 which is connected at oneterminal to the anode of the electron discharge device and at the otherterminal to the cathode thereof through a by-pass condenser 8.

The anode circuit of the oscillator is tuned to the desired operatingfrequency by means of variable condenser ID connected between the anodeand cathode of the electron discharge device oscillator I and in shuntwith the coil 6. Similarly, the grid 28 of the oscillator is tuned tothe desired operating frequency by variable condenser I I in shunt withcoil I2, both of which are connected between the cathode and the grid ofthe tube. A high resistance 9 serves as a grid leak and is shunted by aportion of condenser 8, as shown in the drawings. For the production ofoscillations in the circuit, feed back is obtained by means of theinterelectrode capacity of the electron discharge device I. A suitablepolarizing potential is applied to the anode through choke coil I3 whichis connected in series to one winding of a transformer I4 which islocated externally of applicants compact mechanical arrangement. Bymeans of this arrangement oscillations were obtained of the order of 300megacycles, with a maximum variation in frequency of approximately 1% orless, depending upon the percentage of modulation.

When it is desired to use the circuit as a transmitting device, asuitable level of modulation is applied, usually a very low percentageof modulation, to the external transformer I4 over the speech inputcircuit indicated in the drawings. On the other hand, if the circuit isto be used as a receiver, the speech input circuit will become theoutput circuit and the inductance coil 5 will then be coupled to coil I2instead of to coil 6.

The practical embodiment of the invention is shown in the exploded viewof Fig. 1 wherein the upper removable portion illustrates the antenna inthe form of two arms I, 2, each of which are in series with a condenser3, made variable by means of a screw 3' and coupled through connectionsextending through insulators to the.

parallel tuned circuit comprising condenser 4 and inductance 5. As willbe seen, condenser 4 comprises two semi-circular plates which areconnected to the terminals of 5, both plates in turn beingelectrostatically coupled to a larger circular plate whose distance fromthe two semicircular plates can be varied by means of threaded screw I5,with a consequent variation of the capacitance of the condenser 4. Inpractice, the inductance coil 5 comprises one-and-one-half turns of #18copper wire in diameter for the frequency of 300 megacycles. Theelements of the antenna I, 2, tuning condensers 3 and 4, and inductance5 are all mounted on a suitable metallic plate I6 and insulatedtherefrom by means of the porcelain insulators Il. The mounting I6, aswell as the box herein designated I 8, surrounding the main portion ofthe circuit for shielding purposes, should comprise a pure metal of lowelectrical resistivity, such as aluminum or copper. In one successfulembodiment an aluminum was employed for the box I8 and the mounting I6,mainly because of its light weight.

Referring to the lower portion of Fig. 1, it shouldbe noted thatcondensers II) and I I actually comprise two adjustable phosphor bronzesprings II) and II oppositely disposed with respect to a centralmetallic plate I9 which is directly connected to the cathode of theelectron discharge devicel, which in this case comprises an Acorn tubeof the type known in the art as RCA 955, or an A-20l4, or any otherelectron discharge device suitable for operation at these frequencies. Apair of threaded brass screws 20 and 2|, each with an insulatedextension 22, and operable by means of knurled thumb nuts, are employedfor adjusting the capacitance of the condensers l0 and II by means ofvarying the distances between the springs I0 and II and the centralplate [9.

When the upper part of the construction, consisting of the antenna andthe tuned circuits 4, 5, is properly located in position for use withthe aid of screws, not shown, securing the upper and lower portions ofFig. 1 together, inductance coil 5 will be located adjacent to coil 6for magnetic coupling thereto when the circuit is used as a transmitter.Coil 6, it should be noted, also consists of one and one-half turns ofsuitable size wire. When the circuit is used as a receiver, coil 5 maybe shifted slightly to be adjacent coil l2 forelectromagnetic couplingto this last coil. Coil l2 in practice may comprise a single turn wireof suitable size.

In one successful specific embodiment tried out in practice, theelements of the invention had the following values:

Condenser- 8.00005 mfd.

Grid leak 9- 30,000 ohms.

Choke coil I 3fifteen turns of #24 wire on a form one and one-halfinches long and one-quarter inch in diameter.

Coil l 2- one turn of #18 wire.

Coils 5 and 6- each approximately one and onehalf turns of #18 wire,onequarter inch in diameter.

RCA #955 Acorn tube, or A-2014 Acorn tube.

A factor of major importance in the construction of an arrangement inaccordance with the invention is the fact that the leads connecting thevarious elements together are reduced to an absolute minimum, sinceextremely short leads are absolutely necessary in using such a circuitat the extremely high frequencies of the order of 300 megacycles orabove.

In the present invention there are no leads whatsoever between the gridand anode terminals located externally of the envelope of the tube andthe terminals of the condenser plates Hi and I i, inasmuch as theseterminals are designed to be in actual physical contact with one anotherand are so connected. Similarly with respect to the coils 6 and I2. Itwill be observed that one terminal of each of these anode and gridinductances is in actual physical contact with a terminal of thecondensers l0 and H, and if so desired, instead of separate terminalsfor the condensers for both the coils and the tube electrodes, the sameterminals on the condensers may be used for the inductance coils as areused for the electrodes of the vacuum tube.

What is claimed is:

1. In a portable ultra high frequency system, an electron dischargedevice oscillator having an anode, a cathode and a grid, a condensercomprising a central planar metallic element and two metal platesmounted on both'sides of said central element, said oscillator andcondenser being located within a metallic box, means comprisinginsulating rods supported from opposite sides of said box for adjustingthe position of said plates with respect to said central element, aconnection from said central element to said cathode, connections fromsaid plates to said grid and anode,

and an antenna circuit located externally of and mounted on said box andcoupled to the electrodes of said device.

2. A compact high frequency communication apparatus comprising first andsecond removable portions adapted to be attached together, an antenna, atuned circuit, and a condenser serially coupling said antenna and tunedcircuit, all

mounted on said first portion, an electron discharge device includinginductance coils and condensers connecting the electrodes thereoftogether for enabling the generation of oscillations all mounted on saidsecond portion, said tuned circuit of said first portion being soconstructed as to be adjacent and magnetically coupled to one of saidinductance coils of said second portion when both portions are attachedtogether.

3. In a high frequency system, an electron discharge device oscillatorhaving an anode, a cathode and a grid, a condenser comprising a centralplanar metallic element and two metal plates mounted on both sides ofsaid central element, said electron discharge device and condenser beinglocated within a metallic shielding box, means for adjusting theposition of each of said plates with respect to said central element, aconnection from said central element to said cathode, and connectionsfrom said plates to said grid and anode, said means comprising twoadjustable insulating rods supported from opposite sides of said box andcontacting said plates.

4. A system in accordance with claim 3, characterized in this that saidantenna consists of a dipole having two arms each of which is mountedexternally of said first portion and on one side of a metal plate, saidtuned circuit being located on the other side of said metal plate andincluding a condenser whose terminals are coupled to said antennathrough, but insulated from, said plate, and means on the same side ofsaid plate as the antenna, extending through said plate, for adjustingthe capacitance of said last condenser.

5. A compact high frequency communication apparatus comprising ametallic shielding container including first and second removableportions adapted to be attached together, an antenna and a tuned circuitmounted on said first portion, an electron discharge device oscillatorincluding a grid inductance coil and an anode inductance coil mounted onand Within said second portion, said tuned circuit of said first portionbeing so constructed and arranged as to be adjacent and magneticallycoupled to one of said inductance coils of said second portion when bothportions are attached together.

6. A compact high frequency communication apparatus comprising ametallic shielding container including first and second removableportions adapted to be attached together, an antenna and a tuned circuitmounted on said first portion, an electron discharge device oscillatorincluding a grid inductance coil and an anode inductance coil mounted onand within said second portion, said tuned circuit and antenna being soconstructed and arranged that the antenna is located externally of saidcontainer and said tuned circuit adjacent and magnetically coupled tosaid anode inductance coil when both portions are attached together.

ROBERT M. MORRIS.

CAREY P, SWEENY.

